What the FDA labels say about taking them together
Carbamazepine and nelfinavir
Nelfinavir's FDA label of December 11, 2025 names carbamazepine in its drug interactions section; the carbamazepine labels PlainMeds reads (3) do not name nelfinavir. The nelfinavir label: “Concentrations of nelfinavir may be decreased. VIRACEPT may not be effective due to decreased nelfinavir plasma concentrations in patients taking these agents concomitantly. …”
Check it at the source: the carbamazepine FDA label on DailyMed (effective August 20, 2026, Novartis Pharmaceuticals Corporation); the nelfinavir FDA label on DailyMed (effective December 11, 2025, AGOURON).
What does the carbamazepine label say about nelfinavir?
Carbamazepine's label (effective August 20, 2026) and its 2 other brand-application labels do not name nelfinavir in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Tegretol), Novartis Pharmaceuticals Corporation, effective August 20, 2026 (SPL set 8d409411-aa9f-4f3a-a52c-fbcb0c3ec053), via openFDA; the full label on DailyMed
What does the nelfinavir label say about carbamazepine?
Nelfinavir label, drug interactionsConcomitant Drug Class/Drug Name: Carbamazepine Phenobarbital Phenytoin; Effect on Concentration: ↓ nelfinavir ↓ phenytoin; Clinical Comment: Concentrations of nelfinavir may be decreased. VIRACEPT may not be effective due to decreased nelfinavir plasma concentrations in patients taking these agents concomitantly. Phenytoin plasma/serum concentrations should be monitored; phenytoin dose may require adjustment to compensate for altered phenytoin concentration.
Source: FDA drug label (VIRACEPT), AGOURON, effective December 11, 2025 (SPL set e72c2bc6-9462-4a2e-8e1d-b97592376cbd), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Carbamazepine | Nelfinavir | |
|---|---|---|
| Labeled for | Bipolar disorder, Seizures and epilepsy | HIV |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $0.119 per tablet 200 mg tablet | n/a |
| Shortage now | A presentation being discontinued | No current entry |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once